To provide an insight into the effect of the nonlinear strain-softening phenomenon on the mechanical behavior of the surrounding rock mass

an elastoplastic softening model considering softening coefficient is proposed. The approach for calculating the stress and strain states in the surrounding rock of a circular tunnel is presented. Then

by comparing with Brown’s method and converted Mohr-Coulomb failure criterion method

the proposed model is proved to be reasonable. Finally

effects of softening coefficient on the deformation behavior of surrounding rock and the support pressure are studied. The results show that: when the softening coefficient is relatively large

the result by the elasto-brittle-plastic model is basically identical to that by elastoplastic softening model; it is the radius of the loose region that mainly controls the deformation and stability of surrounding rock; the critical support pressure that controls the appearance of plastic region is equal to the radial stress at the elasticplastic boundary quantitatively.